This is embarrassing. I've had this computer for 4.5 years, and I just noticed a button that I never saw before (the guy lives in a fog!). I'm wondering what I'm missing (or what I did when I pushed the button). Anybody know?
State of battery charge. If unplugged, will give you a guesstimate of how much charge is left. If plugged and charging will show you how much has already charged till all 8 dots are green: you'll see each dot start blinking until charged.
More info: http://support.apple.com/kb/HT3205